TOKYO, Nov 7 (Reuters) - Singapore-based fund 3D Investment Partners has urged external directors of Sapporo Holdings to take the lead in reassessing a revitalisation plan for the Japanese beer company, according to a letter reviewed by Reuters.

The fund said in the letter, dated Nov. 3, it was "deeply disappointed" by an Oct. 28 response from the outside directors on the value enhancement plan that 3D had presented. It wasn't immediately clear what the directors' response was, and details of 3D's original proposals weren't immediately available.

The fund has asked the five outside directors to postpone the announcement of a new business plan scheduled on Wednesday, among other requests.

3D Investment Partners and Sapporo Holdings declined to comment on the report.

The fund noted that Sapporo Holdings had failed to meet its sales target during the past 15 years, and that its return on equity (ROE) averaged 2% in the past five years - far lower than rivals Kirin Holdings' 14% and Asahi Group Holdings' 11%, the Nikkei newspaper reported earlier.

Sapporo Holdings was the target of a takeover bid in 2007 by U.S.-based activist fund Steel Partners, which had urged the company to sell off underperforming units and improve management of its real estate holdings.

The buyout failed and Steel Partners sold most of its remaining stake in Sapporo in 2010.

Shares of Sapporo Holdings were up 0.2% in the morning session of Tokyo trade, trailing a 1.7% rise for Kirin and a 1.9% advance by Asahi. (Reporting by Chang-Ran Kim, Rocky Swift and Makiko Yamazaki; Editing by Christian Schmollinger and Kenneth Maxwell)